Antimicrobials target pathogens on produce

A novel food safety treatment tested by Agricultural Research Service (ARS) scientists could become an asset to the fast-growing fresh-cut produce industry.

The antimicrobial treatment involves the use of submicroscopic agents that are unable to reproduce or grow outside bacterial host cells. The purified viral agents are called bacteriophages, which means "bacteria eater," and they can wreak havoc on deadly bacteria, such as E. coli O157:H7, that sicken consumers.

The bacteriophage research is being conducted by microbiologist Manan Sharma, with the ARS Food Safety Laboratory, in Beltsville, Md., in collaboration with researchers at Intralytix Inc., based in Baltimore, Md.

Interest in bacteriophages is ramping up with the emergence of antibiotic-resistant organisms. These "phages" are present in the environment and only attack bacteria; they do not have an adverse effect on humans and animals.

Sharma tested a group of phages (ECP-100) on refrigerated samples of fresh-cut cantaloupe. The treatments reduced pathogens on the samples of fresh-cut cantaloupe by 100-fold in comparison to untreated samples.

Sharma also tested the phages on refrigerated fresh-cut lettuce. The results indicate that bacteriophage treatments can kill E. coli O157:H7 on the surface of leafy green commodities with the same level of efficiency seen in the fresh-cut cantaloupe.

Phages reproduce by latching onto bacteria. The viral DNA is injected into the bacterial hosts' cells, where it directs the production of progeny phages. These phages kill bacterial host cells on exit, and then move on to infect more bacterial cells.

The trials indicated that the phage treatments could be effective in killing E. coli O157:H7 in produce.

ARS is a scientific research agency of the U.S. Department of Agriculture.